you need to consider the cost to get the car in the best condition for the trip vs the cost of a breakdown. Even if you have recovery cover, costs out there will be expensive, not to mention delays for parts etc which can cost you extra in accomodation or a return trip to collect the car. You'll maybe br working the car harder than you usually do, so it's best to cover the critical items if you can. Don't forget to have the relevant safety geaar too, warning triangle, bulb and first aid kit, hi-vis jacket that you can reacn and put on before leaving the car (the french law may be harsh on that front).
Definately drain and refill the cooling system rather than topping up, and change the air filter, can't help on the other standard service items for the 147 though. If changing the belts, probably worth replacing the spark plugs too and check your brakes & fluid levels.